1. Field of the Invention
The present invention relates generally to auxiliary power systems for vehicles, more specifically to power regulation of an auxiliary power unit to operate the auxiliary air conditioning and heating system.
2. Description of the Related Art
Many vehicles in particular truck tractors typically referred to as semi-tractor-trailers are equipped with sleeping and resting compartments. These compartments are provided to save driver the time and expense of procuring local sleeping arrangements during extended down-time and to allow the driver to provide personal security to the vehicle, along with other incidental benefits.
A problem faced by the drivers of these vehicles is that during very warm weather and very cold weather, the drivers have traditionally needed to run their main engines to keep the vehicle cabin area comfortable enough for the driver to obtain adequate rest, to allow the driver amenities such as the ability to watch television or listen to the radio, or to have refrigerated foods. Additionally, particularly in cold weather, when the vehicle is not being driven or stopped briefly, and where external electric power outlets are not readily available to the drivers, the drivers have traditionally needed to run their main engines to assure the engines would maintain sufficient compression and adequate lubrication to restart. Running the main vehicle engine during an extended stop, however, is not only very inefficient, is recognized that it is an environmentally unsound practice, and due to the recent increase in cost of fuel, it is becoming a less financially viable option.
One solution to the problem of maintaining an ergonomic environment for the drivers, and maintaining the ability for the vehicle to restart during cold weather, has been to use an auxiliary power plant consisting of an auxiliary engine and a generator, typically co-positioned with the main vehicle engine to directly power the vehicles air-conditioning, heating, or electrical components normally powered by the main engine. There is, however, limited ability to position such power plant in the main engine compartment. Additionally, positioning such components in the main engine compartment has resulted in increased difficulty of performing maintenance.
A recent innovation in the art has been to position an auxiliary power unit and an existing auxiliary compartment. These units, however, generally only consist of an engine or power plant and a generator and do not provide independent air-conditioning and heating systems and thus, have many of the same maintainability issues as the power plants or power sources positioned in the main engine compartment.
Recognized, therefore, is the need for a compact auxiliary power unit which is generally self-contained and can be housed in an existing or modified auxiliary compartment of the vehicle, and that includes within the auxiliary compartment a generator to provide electric power to power various electronic components in the vehicle cabin, a heating system, an air-conditioning system. Recognized also is the need for an auxiliary power unit which includes sensors and circuitry to monitor and control the electrical components and power requirements.
Another problem faced by drivers employing prior auxiliary power unit systems involve difficulty in starting the units and reduced service life due to the units being subjected to heavy loads during startup. Thus, also recognized is the need for a compact auxiliary power unit which includes an RPM sensor or is equipped with a ramp-up which will prevent excessive load on the engine during startup.
A further problem faced by drivers using auxiliary power systems, similar to those faced by drivers that do not use an auxiliary power source, is that the drivers do not realize they are drawing power over and above that capable of the unit, and thus, deplete the vehicle battery resulting in an inability to start the main engine. Thus, also recognized is the need for a compact auxiliary power unit which includes a voltage or current regulator which will interrupt or limit current output of its power generator to various high-drain electrical components during periods of very high loading to prevent vehicle battery depletion, thus preventing an “engine no-start incident” from occurring.